Re-added setAutoFillBackground(true) in IdealDockWidget, otherwise the widget
ends up being transparent, which sometime results in widget painting
collisions with main panel.

Note that the bug was not visible with oxygen, since it has been modified
(since kde4.4) to still paint the default background gradient (instead of flat
background color), in such cases. All other styles were broken, though.

starting # with '#' will be ignored, and an empty message aborts the commit.